Internal gate valve for flow completion systems

ABSTRACT

A gate valve for a component which includes an elongated body and a flow passage extending generally longitudinally through the body, the flow passage including a generally lateral first branch connected to a generally longitudinal second branch. The gate valve comprises a gate which is moveable generally longitudinally across the first branch between an open position in which a hole in the gate is aligned with the first branch and a closed position in which the hole is offset from the first branch; a conduit which extends through the body from the gate; an actuating mechanism positioned in the conduit for moving the gate from a first position to a second position; and a return biasing mechanism for moving the gate from the second position to the first position; wherein one of the first and second positions corresponds to the open position of the gate and the other position corresponds to the closed position of the gate; and wherein the conduit extends generally longitudinally through the body.

This application is a continuation of U.S. patent application Ser. No.09/815,436 filed on Mar. 22, 2001, now U.S. Pat. No. 6,497,277, which isbased on U.S. Provisional Patent Application No. 60/192,124 filed onMar. 24, 2000.

BACKGROUND OF THE INVENTION

The present invention relates to a gate valve which may be used tocontrol the flow of fluid through various components of a flowcompletion system, such as a tubing hanger. More particularly, theinvention relates to such a gate valve which is remotely operable andwhich is oriented generally longitudinally in the component andtherefore occupies a minimum of the radial cross sectional area of thecomponent.

The need to remotely and reliably control the flow of fluid throughcomponents having relatively small radial cross sectional areas isparticularly strong in the field of flow completion systems forproducing oil or gas from a subsea well. A typical horizontal-type flowcompletion system comprises a wellhead housing which is installed at theupper end of a well bore, a tubing spool which is connected to the topof the wellhead housing and which includes a central bore extendingaxially therethrough, and a tubing hanger which is suspended in thecentral bore and which supports at least one tubing string that extendsinto the well bore and defines a tubing annulus surrounding the tubingstring. The tubing hanger is usually an annular component which includesat least one longitudinal production bore connected to the tubingstring, a lateral production passageway that extends between theproduction bore and a production outlet in the tubing spool, and one ormore service and control conduits for communicating control signals orfluids from external service and control lines to corresponding devicesor positions located in or below the tubing hanger. In addition, thetubing hanger may include a longitudinal annulus bore for connecting thetubing annulus with the portion of the central bore located above thetubing hanger.

In operation of the flow completion system, flow through the annulusbore and the service and control conduits must be carefully controlledto ensure that well fluid does not escape into the environment. Forexample, during installation and workover of the flow completion system,the annulus bore must typically remain closed until a blowout preventer(“BOP”) is installed above the tubing hanger, at which point the tubinghanger may be opened to allow for circulation of fluid between theproduction bore and the tubing annulus. In the prior art, a wirelineplug is typically used to close the annulus bore. However, eachinstallation or removal of the plug requires a special trip from asurface vessel. Moreover, although several versions of remotely operablevalves for controlling flow through the annulus bore have been patented,these valves have for the most part been impractical to implement due tothe limited radial cross sectional area that is available in the tubinghanger for such valves.

Therefore, a need exists for a remotely operable valve which canreliably control the flow of fluid through a flow completion systemcomponent but which occupies a minimum radial cross sectional area ofthe component.

SUMMARY OF THE INVENTION

In accordance with the present invention, these and other disadvantagesin the prior art are overcome by providing a closure member for acomponent having an elongated body and a flow passage extendinggenerally longitudinally through the body, the flow passage including agenerally lateral first branch connected to a generally longitudinalsecond branch. The closure member comprises a gate which is moveablegenerally longitudinally across the first branch between an openposition in which a hole in the gate is aligned with the first branchand a closed position in which the hole is offset from the first branch,a conduit which extends through the body from the gate, an actuatingmechanism positioned in the conduit for moving the gate from the closedposition to the open position, and a return biasing mechanism for movingthe gate from the open position to the closed position, wherein theconduit extends generally longitudinally through the body. In apreferred embodiment of the invention the actuating mechanism comprisesa piston which is connected to the gate and which sealingly engages theconduit, and means for conveying hydraulic pressure to a first portionof the conduit which communicates with the piston.

Thus, it may be seen that the components of the closure member whichmove the gate are aligned generally longitudinally relative to the gate.In this manner, the closure member occupies a minimum amount of thelateral cross sectional area of the component compared to prior artclosure members. In addition, since hydraulic pressure is used toactuate the gate, the closure member may be operated remotely.

In one embodiment of the present invention, the closure member isadapted for use in a tubing hanger which is suspended in a tubing spooland which comprises an elongated body having an annulus bore thatextends generally axially therethrough, the annulus bore comprising agenerally lateral first branch connected to a generally axial secondbranch. Accordingly, the closure member comprises a gate which ismoveable generally axially across the first branch between an openposition in which a hole in the gate is aligned with the first branchand a closed position in which the hole is offset from the first branch,a conduit which extends generally axially through the body from thegate, an actuating mechanism positioned in the conduit for moving thegate from the closed position to the open position, and return biasingmechanism for moving the gate from the open position to the closedposition. In a preferred embodiment of the invention, the actuatingmechanism comprises a piston which is connected to the gate and whichsealingly engages the conduit, and means for conveying hydraulicpressure to a first portion of the conduit which communicates with thepiston. Furthermore, the tubing hanger ideally comprises first andsecond annular seals positioned between the body and the tubing spool,and the closure member further comprises a gate cavity in which the gateis at least partially positioned and which extends into the body frombetween the first and second seals, wherein pressure within the gatecavity is contained by the first and second seals.

Therefore it may be seen that the closure member of the presentinvention permits flow through the tubing hanger annulus bore to bereliably controlled from a remote location without the use of wirelineplugs. Furthermore, since the gate and its actuating mechanism areoriented generally axially within the tubing hanger, the closure memberoccupies a minimum radial cross-sectional area of the tubing hanger.

These and other objects and advantages of the present invention will bemade apparent from the following detailed description, with reference tothe accompanying drawings. In the drawings, the same reference numbersare used to denote similar components in the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of an exemplary flowcompletion system which comprises the gate valve of the presentinvention;

FIG. 2 is a longitudinal cross-sectional view of a portion of the tubinghanger component shown in FIG. 1 taken through the tubing hanger annulusbore and the gate valve;

FIG. 3 is an enlarged longitudinal cross-sectional view of the gatevalve shown in FIG. 2;

FIG. 4 is a radial cross-sectional view of a portion of the tubinghanger component and the gate valve shown in FIG. 1;

FIG. 5 is a longitudinal cross-sectional view of the gate and seatcomponents of the gate valve of the present invention;

FIG. 6 is a longitudinal cross-sectional view of a portion of the tubinghanger component shown in FIG. 1 taken through the tubing hanger annulusbore and another embodiment of the gate valve of the present invention;

FIG. 7A is a longitudinal cross-sectional view of the male overridecoupler of the gate valve depicted in FIG. 6 shown in its normal mode ofoperation;

FIG. 7B is a longitudinal cross-sectional view of the male overridecoupler of the gate valve depicted in FIG. 6 shown in its manualoverride mode of operation;

FIG. 8A is a longitudinal cross-sectional view of the annulus boreprotector component depicted in FIG. 6 shown in its up position;

FIG. 8B is a longitudinal cross-sectional view of the annulus boreprotector component depicted in FIG. 6 shown in its home position;

FIG. 8A is a longitudinal cross-sectional view of the annulus boreprotector component depicted in FIG. 6 shown in its down position; and

FIG. 9 is a partial longitudinal cross-sectional view of anotherembodiment of a gate valve assembly of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the gate valve assembly of the present invention may be used tocontrol flow through a variety of flow completion system components, itwill be described hereafter in connection with the tubing hangercomponent of an exemplary flow completion system.

Referring to FIG. 1, a preferred embodiment of the gate valve 10 isshown installed in an exemplary flow completion system 12. As explainedmore fully in applicants' co-pending U.S. patent application Ser. No.09/815,437, which is hereby incorporated herein by reference, the flowcompletion system 12 comprises a wellhead housing 14 which is installednear the top of a well bore (not shown), a tubing spool 16 which isconnected over the wellhead housing 14 and which includes a central bore18 that extends axially therethrough, and a tubing hanger 20 which issupported in the central bore 18 and which includes a generally annularbody 22 having an outer, stepped cylindrical wall 24. The tubing hanger20 supports at least one tubing string 26 which extends into the wellbore and defines a tubing annulus 28 surrounding the tubing string. Inaddition, the tubing hanger 20 includes a concentric production bore 30which communicates with the tubing string 26, a lateral productionpassageway 32 which extends between the production bore 30 and aproduction outlet 34 in the tubing spool 16, an annulus bore 36 whichextends generally axially between the tubing annulus 28 and a portion ofthe central bore 18 located above the tubing hanger, and a number ofservice and control conduits 38 which extend generally axially throughthe tubing hanger. The flow completion system may also comprise one ormore valves 40 for controlling flow through the production outlet 34,and a controls bridge 42 for connecting the annulus bore 36 and theservice and control conduits 38 with corresponding external service andcontrol lines (not shown).

In the flow completion system 12 depicted in FIG. 1, the tubing hanger20 preferably also includes both of the industry required first andsecond barriers between the well bore and the environment, thuseliminating the need for a separate pressure sealing tree cap. The firstbarrier is provided by a first wireline crown plug 44 that is disposedin the production bore 30 above the production passageway 32, and afirst annular, preferably metal seal 46 which is positioned between thetubing hanger 20 and the tubing spool 16 above the productionpassageway. Similarly, the second barrier is provided by a secondwireline crown plug 48 that is mounted in the production bore 30 abovethe first crown plug 44, and a second annular, preferably metal seal 50which is positioned between the tubing hanger 20 and the tubing spool 16above the first seal 46. In accordance with the present invention, thetubing hanger 20 also includes the gate valve 10 and, in the embodimentof the invention depicted in FIG. 1, preferably also a second closuremember 52, such as a sting open check valve, for controlling fluid flowthrough the annulus bore 36.

Referring to FIGS. 2-5, the gate valve 10 is unique in thatsubstantially all of its operational components are housed entirelywithin the body 22 of the tubing hanger 20. In addition, the gate valve10 is oriented generally axially within the tubing hanger 20 so as tooccupy a minimum of the radial cross sectional area of the tubinghanger. In order to most readily accommodate this vertical orientationof the gate valve 10, the annulus bore 36 preferably includes a lateralbranch which is connected to a longitudinal branch, and the gate valveis disposed across the lateral branch. For example, in the embodiment ofthe invention depicted in FIGS. 2-5, the annulus bore 36 is shown tocomprise an upper branch 54 which extends generally axially through thebody 22 to the top of the tubing hanger 20, a lower branch 56 whichextends generally axially through the body to the bottom of the tubinghanger, and an intermediate branch 58 which extends generally laterallybetween the upper and lower branches. To facilitate the formation of theannulus bore 36, the intermediate branch 58 is ideally machined into theouter wall 24 and then sealed by a plug member 60 or any other suitablemeans.

In the embodiment of the invention depicted in FIGS. 2-5, the gate valve10 is shown to comprise a generally rectangular gate cavity 62 whichextends generally laterally through the outer wall 24 of the tubinghanger 20 and intersects the intermediate branch 58. In addition, anannular seat pocket 64 extending transversely into the body 22 ispreferably formed at each intersection of the gate cavity 62 with theintermediate branch 58. The gate valve 10 also comprises two ring-shapedseats 66, each of which is positioned in a seat pocket 64, a gate 68which is slidably disposed between the seats 66, and an actuatingmechanism 70 which is positioned substantially in a service and controlconduit 38 that extends generally axially over the gate cavity 62.

Referring specifically to FIG. 5, each seat 66 is preferably a floatingseat which comprises a front face 72 that engages the gate 68, a rearface 74 opposite the front face, a generally cylindrical outer wall 76,and a coaxial through bore 78 that aligns with the intermediate branch58. The outer wall 76 optimally comprises an enlarged diameter rim 80adjacent the front face 72, a reduced diameter portion 82 adjacent therear face 74, and a shoulder 84 located between the rim and the reduceddiameter portion. In addition, a Belleville washer 86 or similar meansis positioned between the rim 80 and the wall of the gate cavity 62 tourge the seat 66 against the gate 68, and an annular seal 88, such as aspring energized, pressure intensified straight bore-type seal, isdisposed around the reduced diameter portion 82 to seal between the seatand the seat pocket 64. The seal 88 is preferably oriented so as to beenhanced by pressure in the gate cavity 62, and a spacer ring 90 havinga plurality of radial holes extending therethrough may be placed betweenthe seal and the shoulder 84 to maintain the seal properly positionedrelative to the seat. Also, the rear face 74 is preferably rounded toform a circular sealing lip 92 to provide an additional seal, this onemetallic, between the seat 66 and the seat pocket 64.

The actuating mechanism 70 functions to move the gate 68 between a valveopen position, in which a transverse hole 94 in the gate is aligned withthe intermediate branch 58, and a valve closed position, in which thehole 94 is offset from the intermediate branch (as shown in FIGS. 2 and5). In a preferred embodiment of the invention, the actuating mechanism70 comprises a piston head 96 which supports a piston seal 98 thatengages the service and control conduit 38, an elongated piston rod 100which is connected to the bottom of the piston head 96, and a valve stem102 which is attached between the lower end of the piston rod 100 andthe top of the gate 68, for example via a T-slot connection 104. Also, asuitable stem packing 106 is positioned between the valve stem 102 andthe service and control conduit 38 to seal the gate cavity 62 from theportion of the service and control conduit located above the packing.The packing is ideally held in place by a gland nut 108 that is securedto the body 22 of the tubing hanger 20 by suitable means, such as aretainer screw 110. The actuating mechanism 70 preferably also includesa return biasing mechanism, which in the embodiment of the inventionillustrated in FIGS. 2 and 3 comprises a mechanical biasing means 112,such as a stack of Belleville washers, that is operatively engagedbetween the piston head 96 and the gland nut 108.

In one embodiment of the present invention, the gate cavity 62 extendsinto the body 22 of the tubing hanger 20 between the first and secondannular seals 46, 50 and consequently forms an opening 114 in the wall24 that is positioned between the seals. The opening 114 is optimallyclosed by a simple cover plate 116 which is held in place by acylindrical sleeve 118 that is telescopically received over the tubinghanger 20. The pressure within the gate cavity 62 is preferablycontained by the first and second seals 46, 50 and the stem packing 106.Therefore, no need exists for a separate seal or seals between the coverplate 116 and the body 22 to contain the pressure within the gate cavity62. However, the present invention contemplates that one or more suchseals could be provided between the body 22 and either the cover plate116 or the sleeve 118, to contain the pressure within the gate cavity62, especially when the opening 114 is not located between the seals 46,50. In addition, instead of the cover plate 116 being retained by thesleeve 118, the sleeve could be dispensed with and the cover platesimply bolted onto the body, in which event seals are preferablyprovided between the cover plate and the body 22 to retain the pressurewithin the gate cavity 62.

In the production mode of operation of the flow completion system 12,the gate valve 10 is normally in the closed position. When it is desiredto open the annulus bore 36, a pressure sufficient to overcome thecombined force of the mechanical biasing means 112 and the friction atthe various interfaces of the gate valve 10 is introduced into theservice and control conduit 38 above the piston head 96. This pressurewill force the piston head 96 downward and thus move the gate 68 intothe open position. In this position, fluid in the tubing annulus 28 isallowed to flow from the lower branch 56, through the intermediatebranch 58 and into the upper branch 54, where it will encounter thesecond closure member 52, if present.

As shown in FIG. 2, a male coupling 120 of a conventional hydrauliccoupler may be installed in the top of the service and control conduit38 to facilitate connecting a source of high pressure hydraulic fluid tothe service and control conduit. The male coupling 120 is engaged by acorresponding female coupling (not shown), which may be mounted, forexample, in a tubing hanger running tool or the controls bridge 42 andwhich in turn is connected to the pressure source by a correspondingexternal service and control line. Alternatively, the top of the serviceand control conduit 38 may include a seal profile for a stab which iscarried on the tubing hanger running tool or the controls bridge andwhich in turn is connected to the pressure source. The gate valve 10 mayalso comprises a compensation port 122 that extends through the body 22of the tubing hanger 20 between the top of the tubing hanger and aportion of the service and control conduit 38 which is located below thepiston head 96. While not shown in the drawings, a male coupling or stabseal profile may be provided at the top of the compensation port 122 tofacilitate the connection of this port through the tubing hanger runningtool or the controls bridge to a corresponding external service andcontrol line.

When it is desired to close the gate valve 10, the pressure is removedfrom the service and control conduit 38, whereupon the force from themechanical biasing means 112 combined with the pressure in the annulusbore 36 acting on the valve stem 102 will push the piston head 96 upwardand move the gate 68 into the closed position. If the means supplyingthe pressure to the service and control conduit 38 should fail for anyreason, the mechanical biasing means 112 will either retain the gate 68in the closed position or move the gate from the open position to theclosed position. Thus, in the preferred embodiment of the invention thegate valve 10 is a “fail closed” device.

In an alternative embodiment of the gate valve 10, the actuatingmechanism 70 is a pressure balanced device. Thus, the return biasingmechanism would not require a mechanical biasing means 112. Instead, thecompensation port 122 is connected to a source of high pressurehydraulic fluid. In order to return the gate valve 10 to the closedposition, pressure is introduced into the compensation port 122 to forcethe piston head 96, and thus the gate 68, upward. In this embodiment,the gate valve 10 is a “fail as is” device.

In accordance with another embodiment of the present invention, which isillustrated in FIG. 6, the actuating mechanism 70 may comprise amechanical override feature to allow the gate valve to be actuatedmechanically, for example in the event of a failure relating to thepressure source. This mechanical override feature is provided by a maleoverride coupling 124 that is mounted in the top of the service andcontrol conduit 38. During normal operation, the override coupling 124conveys high pressure fluid to the service and control conduit 38 tohydraulically force the piston head 96 downward. However, in the eventof a failure relating to the pressure source, an external actuator canpush a portion of the override coupling 124 downward into engagementwith the piston head 96 to mechanically force the piston head downward.

Referring to FIG. 7A, the override coupling 124, which is shown in itsnormal mode of operation, may be seen to comprise a coupling sleeve 126which is movably retained within the service and control conduit 38 by aretainer sleeve 128. The coupling sleeve 126 comprises a stem 130 whichincludes an axial passage 132 and a number of radial ports 134 thatconnect the axial passage with the exterior of the stem, an upperreceptacle 136 which is connected to the axial passage, and a lowerreceptacle 138 in which the piston head 96 is slidably received andagainst which the piston seal 98 is sealably engaged. The overridecoupling 124 also comprises a valve sleeve 140 which is slidablyreceived in the upper receptacle 136 and is sealed therein by a ringseal 142, a keeper 144 which is secured in the upper receptacle belowthe valve sleeve, a valve pin 146 which is supported in the keeper andwhich extends longitudinally through a lower cavity 148 that is formedin the valve sleeve 140, and a return spring 150 which is positioned inthe lower cavity between the keeper and the valve sleeve to urge thevalve sleeve upwards against the top of the upper receptacle 136. Thevalve sleeve 140 also includes an upper cavity 152, an orifice 154 whichextends between the upper cavity and the lower cavity 148, and anannular valve seat 156 that is formed between the upper cavity and theorifice. In addition, the upper cavity 152 houses a valve head 158 whichis urged into sealing engagement with the valve seat 156 by a reliefspring 160 that is supported in the upper cavity by a retainer ring 162.

In order to open the gate valve 10 during normal operation of theoverride coupling 124, a female coupling (not shown) is coupled to thestem 130 and pressurized hydraulic fluid is conveyed from the femalecoupling into the ports 134, through the axial passage 132 and into theupper cavity 152 of the valve sleeve 140. This pressure forces the valvesleeve 140 downward against the return spring 150, but the valve head158 is prevented from moving downward by the valve pin 146. Instead, thevalve head 158 separates from the valve seat 156 and allows thehydraulic fluid to flow through the orifice 154. The hydraulic fluidflows into the lower cavity 148, through an opening in the keeper 144(not shown) and into the lower receptacle 138, where it will force thepiston head 96 downward to open the valve.

In order to open the gate valve 10 in the manual override mode ofoperation of the override coupling 124, which is depicted in FIG. 7B, andevice such as a stab plate attached to a tubing hanger running tool ispressed against the top of the stem 130 to push the coupling sleeve 126downward. As a result, the bottom of the coupling sleeve 126 willcontact the piston head 96 and force it downward, which will therebyopen the gate valve.

Referring again to FIG. 7A, the override coupling 124 preferablyincludes a relief mechanism to prevent pressure from being trapped inthe lower receptacle 138. Such trapped pressure could interfere with thereturn of the piston head 96 and thereby prevent the gate valve 10 fromclosing properly. In the absence of pressure in the upper cavity 152 ofthe valve sleeve 140, any pressure within the lower receptacle 138 willforce the valve head 158 off the valve seat 156 and against the reliefspring 160. The pressure will consequently be allowed to pass throughthe orifice 154 and exit the override coupling through the axial passage132 and the radial ports 134.

In the embodiment of the invention illustrated in FIG. 6, the flowcompletion system 12 may include a debris valve 164 in the upper branch54 of the annulus bore 36 to prevent debris from collecting in theannulus bore. Referring to FIG. 8A, in order to accommodate the debrisvalve 164 the upper branch 54 ideally includes an upper expansion 166and a lower expansion 168. Also, the debris valve 164 comprises a hollowcylindrical body 170 which is slidably received in the annulus bore, anannular collar 172 which is secured in the annulus bore between theupper and lower expansions, and a spring 174 which is operativelyengaged between a shoulder in the annulus bore and a radial flange 176extending from the body. In addition, the body 170 includes a closed topend 178, an open bottom end 180 and a number of lateral ports 182 whichcommunicate with the interior of the body.

When the annulus bore 36 is closed, the spring 174 will urge the body170 into the home position, in which the top end 178 is positionedwithin the collar 172 (FIG. 8B). In this position, debris is preventedfrom passing past the top end and into the annulus bore. If fluid isallowed to flow up through the annulus bore, the fluid will force thebody 170 into the up position, in which the flange 176 is in contactwith the collar 172 and the ports 182 are positioned at least partiallyin the upper expansion 166 (FIG. 8A). In this position, the fluid isallowed to flow up through the bottom end 180, out the ports 182,through the upper expansion 166 and up through the annulus bore. Iffluid is forced down through the top of the annulus bore, the fluid willforce the body 170 into the down position, in which the flange 176 isforced down against the spring and the ports 182 are positioned at leastpartially in the lower expansion (FIG. 8A). In this position, the fluidis allowed to flow past the lower expansion 168, in through the ports182, out through the bottom end 180 and down through the annulus bore.

Referring now to FIG. 9, another embodiment of a gate valve of thepresent invention, which is indicated generally at 10′, is showninstalled in an exemplary tubing hanger 20. In this embodiment thetubing hanger 20 is shown to comprise an annulus bore 36 having a firstbranch 184 which extends generally laterally through the tubing hangerfrom the tubing annulus 28, and a second branch 186 which extends fromthe first branch to the top of the tubing hanger. In addition, the gatevalve 10′ comprises a gate cavity 62 that extends laterally through thewall 24 of the tubing hanger generally coaxially with the first branch184. The gate cavity 62 forms an opening 114 in the wall 24 which ispreferably closed by a cover 188 that is ideally removably attached tothe tubing hanger using any suitable means, such as bolts (not shown).In addition, the cover 188 is optimally sealed to the tubing hanger withat least one annular seal 190.

In the embodiment of the invention depicted in FIG. 9, the gate valve10′ is shown to comprise a gate 68 which is slidably disposed across thefirst branch 184 between a pair of seats 192, 194. The first seat 192 issimilar to the seats 66 discussed above. The second seat 194 can beidentical to the first seat 192 or, as shown in FIG. 9, it can comprisean annular body which is attached to or formed integrally with the cover188. In either event, the cover 188 preferably includes a port 196 whichaligns with the through bores in the seats 192, 194 to define a flowpassage 198 through the gate valve 10′ which extends between the tubingannulus 28 and the first branch 186.

The gate valve 10′ further includes an actuating mechanism to move thegate 68 between a closed position, in which a lateral hole 94 in thegate is offset from the flow passage 198, to an open position, in whichthe hole 94 is aligned with the flow passage, as shown in FIG. 9. Theactuating mechanism (not shown) is positioned in a service and controlconduit 38 that is oriented generally vertically over the gate 68. Inaddition, the actuating mechanism, which can be similar to any of theactuating mechanisms discussed above, is connected to the gate 68 via avalve stem 102.

Although not illustrated in FIG. 9. it should be understood that otherconfigurations of the gate valve are within the scope of the presentinvention. For example, the gate cavity 62 could extend longitudinallyinto the tubing hanger from the bottom thereof. Thus, the gate cavitywould intersect the first branch 184 and provide a convenient means forinstalling the seats in the first branch. In this example, the coverwhich is used to close the opening that the gate cavity makes in thebottom of the tubing hanger would not include a port 196. Rather, thefirst branch 184 would communicate directly with the tubing annulus 28through the wall 24 of the tubing hanger.

Also, although not depicted in the Figures, other configurations of theannulus bore 36 are considered to be within the scope of the presentinvention. For example, the first branch of the annulus bore couldextend generally laterally through the tubing hanger and communicatewith the portion of the central bore of the tubing spool that is locatedabove the seals which are employed to seal the tubing hanger to thetubing spool. In this example, the second branch would extend generallylongitudinally from the first bore down through the tubing hanger to thetubing annulus. In addition, the gate valve would preferably beinstalled in or near the top of the tubing hanger.

It should be appreciated that the gate valve of the present inventionprovides an effective and efficient means for controlling fluid flowthrough the annulus bore 36. The gate valve is recognized in theindustry as being a robust and reliable closure member. Moreover, sincethe gate valve may be operated remotely, the time and expense associatedwith running and retrieving wireline plugs to control fluid flow throughthe annulus bore are eliminated. Furthermore, because the gate valve isoriented generally axially in the tubing hanger, it occupies a minimumradial cross-sectional area of the tubing hanger and therefore allowsthe tubing hanger to comprise a relatively large production bore andseveral service and control conduits.

It should be recognized that, while the present invention has beendescribed in relation to the preferred embodiments thereof, thoseskilled in the art may develop a wide variation of structural andoperational details without departing from the principles of theinvention. For example, the various elements illustrated in thedifferent embodiments may be combined in a manner not illustrated above.Therefore, the appended claims are to be construed to cover allequivalents falling within the true scope and spirit of the invention.

What is claimed is:
 1. In combination with a component having anelongated body and a flow passage extending generally longitudinallythrough the body, the flow passage including a generally lateral firstbranch connected to a generally longitudinal second branch, closuremember comprising: a gate which is moveable generally longitudinallyacross the first branch between an open position in which a hole in thegate is aligned with the first branch and a closed position in which thehole is offset from the first branch; a conduit which extends throughthe body from the gate; actuating mean positioned in the conduit formoving the gate from a first position to a second position; andreturning mean for moving the gate from the second position to the firstposition; wherein one of the first and second positions corresponds tothe open position of the gate an the other position corresponds to theclosed position of the gate; wherein the conduit extends generallylongitudinally through the body, whereby the actuating means isgenerally aligned with the flow passage; and wherein the first andsecond branches are configured and connected such that, when the gate isin its closed position, fluid flow through the flow passage is blocked.2. The closure member of claim 1, wherein the actuating means comprises:a piston which is connected to the gate and which sealingly engages theconduit; and means for conveying hydraulic pressure to a first portionof the conduit which communicates with the piston.
 3. The closure memberof claim 2, wherein the returning means comprises a mechanical biasingmeans.
 4. The closure member of claim 2, wherein the returning meanscomprises means for conveying hydraulic pressure to a second portion ofthe conduit which is separated from the first portion of the conduit bythe piston.
 5. In combination with a tubing hanger which is suspended ina tubing spool and which comprises an elongated body having an annulusbore that extends generally axially therethrough, the annulus borecomprising a generally lateral first branch connected to a generallyaxial second branch, a closure member comprising: a gate which ismoveable generally axially across the first branch between an openposition in which a hole in the gate is aligned with the first branchand a closed position in which the hole is offset from the first branch;a conduit which extends generally axially through the body from thegate; actuating means positioned in the conduit for moving the gate froma first position to a second position; and returning means for movingthe gate from the second position to the first position; wherein one ofthe first and second positions corresponds to the open position of thegate and the other position corresponds to the closed position of thegate.
 6. The closure member of claim 5, wherein the actuating meanscomprises: a piston which is connected to the gate and which sealinglyengages the conduit; and means for conveying hydraulic pressure to afirst portion of the conduit which communicates with the piston.
 7. Theclosure member of claim 6, wherein the returning means comprises amechanical biasing means.
 8. The closure member of claim 6, wherein thereturning means comprises means for conveying hydraulic pressure to asecond portion of the conduit which is separated from the first portionof the conduit by the piston.
 9. The closure member of claim 5, whereinthe tubing hanger comprises first and second annular seals positionedbetween the body and the tubing spool and the closure member furthercomprises: a gate cavity in which the gate is at least partiallypositioned and which extends into the body from between the first andsecond seals; wherein pressure within the gate cavity is contained bythe first and second seals.
 10. In combination with a flow completionsystem which comprises a component having an elongated body and a flowpassage extending generally longitudinally through the body, the flowpassage including a generally lateral first branch connected to agenerally longitudinal second branch, a closure member comprising: agate which is moveable generally longitudinally across the first branchbetween an open position in which a hole in the gate is aligned with thefirst branch and a closed position in which the hole is offset from thefirst branch; a conduit which extends through the body from the gate;actuating mean positioned in the conduit for moving the gate from afirst position to a second position; and returning mean for moving thegate from the second position to the first position; wherein one of thefirst and second positions corresponds to the open position of the gatean the other position corresponds to the closed position of the gate;wherein the conduit extends generally longitudinally through the body,whereby the actuating means is generally aligned with the flow passage;and wherein the first and second branches are configured and connectedsuch that, when the gate is in its closed position, fluid flow throughthe flow passage is blocked.
 11. The flow completion system of claim 10,wherein the actuating means comprises: a piston which is connected tothe gate and which sealingly engages the conduit; and means forconveying hydraulic pressure to a first portion of the conduit whichcommunicates with the piston.